The broad objectives of the proposed project are to gain some insight into the possible function of some of the low molecular weight nuclear RNAs in mammalian cells, in particular C and D RNA, and to examine some of their apparently unusual properties, like their gene organization. Our data on the UV sensitivity of C and D RNA synthesis suggest that these small (less than 0.2 kb) RNAs are synthesized from large (less than 5 kb) transcription units, with either 1 or over 7 genes per transcription unit. We wish to analyze the arrangement of their repetitive genes with several restriction endonucleases. We will attempt to make antibodies against C and D RNA and then apply them to several questions: a) in vivo effect on RNA synthesis, maturation and transport, and protein synthesis; and b) maturation and subcellular localization of RNA species C and D. A third goal is to probe further into the reported association of C and D RNA with heterogeneous nuclear-RNA protein particles.